M87: A Misaligned BL Lacertae Object?
M87: A Misaligned BL Lacertae Object?
复制标题
M87：错位的 BL 蜥蜴物体？
DOI：
10.1086/311139
复制
发表时间：
1997
期刊：
影响因子：
--
通讯作者：
R. Harms
中科院分区：
文献类型：
--
作者：
Z. Tsvetanov;G. Hartig;H. Ford;M. Dopita;G. Kriss;Y. Pei;L. Dressel;R. Harms
1993年12月，在哈勃太空望远镜（HST）上安装了校正光学系统（COSTAR），改善了HST的成像质量后，用暗天体光谱仪（FOS）对M87的核区进行了6次观测，历时18个月。从FOS目标采集数据中，我们已经确定M87光核的通量在2.5个月的时间尺度上变化了约2倍，在3周内变化了25%，在1天的时间尺度上保持不变（约2.5%）。这种变化发生在一个直径小于5pc的中心区域，发射区的物理大小受观测到的时间尺度限制在几百个重力半径内。无特征的连续光谱变得更蓝，因为它变亮，而发射线保持不变。这种可变性，结合对连续光谱形状的观测，强相对论增强，以及对喷流中显著超光速运动的探测，强烈表明M87属于BL Lac类天体，但观测角度太大，无法揭示BL Lac的经典特性。
The nuclear region of M87 was observed with the Faint Object Spectrograph (FOS) on the Hubble Space Telescope (HST) at six epochs, spanning 18 months, after the HST image quality was improved with the deployment of the corrective optics (COSTAR) in 1993 December. From the FOS target acquisition data, we have established that the flux from the optical nucleus of M87 varies by a factor of ~2 on timescales of ~2.5 months and by as much as 25% over 3 weeks and remains unchanged (≲2.5%) on timescales of ~1 day. The changes occur in an unresolved central region ≲5 pc in diameter, with the physical size of the emitting region limited by the observed timescales to a few hundred gravitational radii. The featureless continuum spectrum becomes bluer as it brightens while emission lines remain unchanged. This variability, combined with the observations of the continuum spectral shape, strong relativistic boosting, and the detection of significant superluminal motions in the jet, strongly suggest that M87 belongs to the class of BL Lac objects but is viewed at an angle too large to reveal the classical BL Lac properties.